2002 Sabru Impreza fuel gauge problem

I recently took a road trip and realized that my fuel gauge was going wacky. After about 175 miles the gauge began to rise back to full. At about 200 miles it fell to empty and my fuel light came on. Then within about 5 miles it went to half, then back to full. I stopped to refuel and see if maybe it would go back to normal but it has remained at full for the last two tanks of gas. What would cause this? How do I repair it and what should it cost?

It sounds like the sending unit located in the tank is flukey. IIRC, this can be accessed by removing the rear seat and taking off an access cover.

As to the cost, this will vary a lot, depending on where you live and what type of repair place you take the car to. I would expect that this would cost you somewhere in the neighborhood of $200-$250 for parts and labor if the sending unit can be accessed from underneath the rear seat. If the tank has to be dropped for this job, the cost will be HUGE, due to the location and design of the fuel tank.